Dual vessel reactor

ABSTRACT

A dual vessel reactor and a method of carrying out a reaction using a dual vessel reactor are provided using a non-condensable gas to substantially isolate the inner vessel from the outer vessel during the reaction and limit the heating of the outer vessel when steam from the inner vessel condenses on the interior surface of the outer vessel. By limiting the heating of the outer vessel through the condensation of the steam or other vapour from the inner vessel, the operating temperature of the outer vessel is kept below an upper threshold of the operating temperature of a seal used to seal the door in the outer vessel.

FIELD OF THE INVENTION

The invention relates to a reactor for high pressure and hightemperature reactions and more specifically to a dual vessel reactor.

BACKGROUND

Many reactions require high temperatures and pressures to take place andare therefore carried out in a reactor. As a result, reactors typicallyhave an outer pressure vessel for withstanding the pressure in thereactor. A dual vessel reactor has an inner vessel in which the reactionmay be carried out. The inner vessel is heated to a reaction temperatureeither by an external source or by the reaction itself. The outer vesselis typically a pressure vessel and has a relatively large thickness ascompared to the inner vessel wall so that the reactor can handleelevated reaction pressures.

Some chemical reactions, for example, the devulcanization of rubber,require temperatures as high as 350° C. As a result, a door in the outervessel requires that a metal ring be used to seal the door with thereactor when in the closed position. A rubber seal cannot be used as thehigh temperatures of the reactor and specifically the outer vesseldamage the seal and can cause failure of the seal which is costly andcreates safety issues when the pressure can no longer be contained.

Metal seals, such as metal American Petroleum Institute (API) rings, arecostly, can only be used once, and therefore drive up the cost ofrunning a reaction in a reactor. Furthermore, reactors having outervessels that experience higher operating temperatures, experience higherrates of corrosion on the metals used in the outer vessel and thereforerequire the use of costly metals such as stainless steel or otherequivalent costly alloys in fabrication. Any increase in temperature ofthe outer vessel increases the corrosion rate. Furthermore, conventionalcoatings, such as paints, that can be used to protect steel at elevatedtemperatures are difficult to find.

Water cooling the seal is a possibility, and water cooled seals areavailable. However water cooling the large metal flange which houses theseal will result in the flange operating at lower temperatures and as aconsequence will cause a substantial amount of condensation onto it, andheat transfer to it. Ignoring for a minute the costs associated withthis heat loss, such a loss of heat will ultimately limit the operatingtemperature of the reactor, that is, the heat that is being added toheat the vessel is being lost through condensation on the flange. As aresult, water cooling the seal is undesirable.

A need therefore exists for a dual vessel reactor for use in reactionshaving a high reaction temperature, having an outer vessel suitable foroperation with a non-metal seal and a method of carrying out a reactionin a reactor wherein the outer vessel of the reactor does not exceed anoperating temperature of a non-metal seal or has an operatingtemperature lower than the reaction temperature.

SUMMARY

In one illustrative embodiment there is provided a dual vessel chemicalreactor comprising:

-   -   an outer vessel;    -   a reactor lid on the outer vessel, the reactor lid openable for        accessing the inner vessel;    -   an inner vessel within the outer vessel for containing a liquid,        the inner vessel in atmospheric communication with the outer        vessel;    -   a heat source for heating a liquid in the inner vessel;    -   a seal for sealing the reactor lid with the outer vessel when in        a closed position;    -   an inner vessel lid for covering the inner vessel;    -   wherein during operation a non-condensable gas is used to        substantially insolate the outer vessel from the inner vessel.

In another illustrative embodiment, the reactor as described abovefurther comprises:

-   -   a non-condensable gas input for inputting the non-condensable        gas into the outer vessel.

In another illustrative embodiment there is provided a method ofmaintaining an outer vessel at a temperature below a reactiontemperature while carrying out a reaction in a dual vessel chemicalreactor, the dual vessel chemical reactor having an inner vessel inatmospheric communication with the outer vessel and substantiallypartitionable from the outer vessel. The method comprises the steps of:adding a non-condensable gas to the reactor; heating a liquid in theinner vessel to generate a vapour; and substantially partitioning thenon-condensable gas in the outer vessel and the vapour in the innervessel.

In another illustrative embodiment there is provided a method ofcarrying out a chemical reaction in a dual vessel chemical reactor, thedual vessel chemical reactor having an inner vessel in atmosphericcommunication with the outer vessel and substantially partitionable fromthe outer vessel. The method comprises the steps of adding anon-condensable gas to the reactor; adding a reactant to a liquid in theinner vessel; heating the liquid in the inner vessel to generate avapour; and substantially partitioning the non-condensable gas in theouter vessel and the vapour in the inner vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a prior art reactor wherein the outer vesselhas an operating temperature exceeding that of the operating temperatureof a rubber seal;

FIG. 2 is an illustrative schematic of one embodiment of a dual vesselchemical reactor; and

FIG. 3 is a graph illustrating test results for operating an embodimentof the reactor at various starting pressures of non-condensable gas overa range of temperatures;

FIG. 4 depicts in a schematic a cross sectional view of an illustrativeinner vessel for use in a dual vessel reactor;

FIG. 5 depicts in a schematic a cross sectional view taken along theline A-A′ in FIG. 4;

FIG. 6 depicts in a schematic a view taken along the line B-B′ in FIG.4;

FIG. 7 depicts in a flow chart an illustrative method of maintaining anouter vessel at a temperature below a reaction temperature; and

FIG. 8 depicts in a flow chart an illustrative method of maintaining anouter vessel at a temperature below a reaction temperature.

DETAILED DESCRIPTION

A dual vessel reactor and a method of carrying out a reaction using adual vessel reactor are provided using a non-condensable gas tosubstantially isolate the inner vessel from the outer vessel during thereaction and limit the heating of the outer vessel when steam from theinner vessel condenses on the interior surface of the outer vessel. Bylimiting the heating of the outer vessel through the condensation of thesteam or other vapour from the inner vessel, the operating temperatureof the outer vessel is kept below an upper threshold of the operatingtemperature of a non-metallic seal such as a rubber seal used to sealthe door in the outer vessel. The lower outer vessel temperature alsoreduces corrosion and allows for more conventional coatings, such aspaints, to be used to protect the metal.

A prior art dual vessel reactor is shown in FIG. 1 in which a reactor 5is shown having an inner vessel 10 within an outer vessel 20. Thereactor 5 has a reactor lid 60 sealed to the outer vessel 20 using ametal API ring 70. A nitrogen environment 25 is established in thereactor 5. A heater 30 heats a liquid in the inner vessel 10 into whicha reaction container may be placed. Heating of the inner vessel 10 andthe inner vessel liquid 15 results in elevated temperature of the outervessel 20 (for example it will rise in temperature until it is at theoperating temperature of the inner vessel) and the necessity of a metalseal, such as the metal API seal 70.

FIG. 2 is an illustrative schematic of one embodiment of a dual vesselchemical reactor 100 wherein during operation a non-condensable gas isused to isolate an inner vessel 120 from an outer vessel 110. Thisisolation resulting in the cooling of the outer vessel 110 will beexplained in more detail below.

The chemical reactor 100 has an inner vessel 120 for containing a liquid115. The liquid 115 may be one of a reaction solvent for eitherdissolving a reactant or suspending a reactant, a solution for providingheat transfer to a reaction container 210 upon heating of the solution,or may be a reactant in liquid phase for reacting with a reactant insuspension or in a reaction container 210. The liquid may be water whichforms steam upon heating or another liquid that forms vapour uponheating. The liquid 115 may be any organic or inorganic liquid,preferably with a boiling point above about 25° C. For the purposes ofthis disclosure, the term steam will be used to encompass both watersteam and liquid vapour.

An outer vessel 110 encapsulates the inner vessel 120 and together witha reactor lid 140 form the pressure vessel for the chemical reactor 100.The outer vessel is typically made of a corrosion resistant alloy of asuitable thickness to withstand reaction pressures experienced during achemical reaction to be carried out in the reactor 100. The outer vesselmay be made from coated steel to resist corrosion and does not have tobe made from costly stainless steel. For example, the outer vessel 110may be made Monel®, Inconel® or Hastelloy®. Some coatings for the outervessel 110 may include plasma, thermal coatings or weld cladding. Thereactor lid 140 may be an automatic lid or a manually operated lidsealed to the outer vessel 110 when in a closed position by a seal 150.The seal 150 may be for example, but not limited, to a rubber o-ring orthe like. As will be appreciated in the art, the use of o-rings dependson the temperature and the chemicals to which they will be exposed. Forsteam and temperatures below 200° C. o-rings made from ethylenepropylene diene M-class rubber (EPDM), silicone rubber, Kalrex®,polyacrylate, Viton®, flurosilicone or Aflaf™ are available. The optionsbecome even wider if the outer vessel 110 is kept below 100° C.throughout the reaction. If necessary, the outer vessel 110 may becooled so it does not go above a predetermined temperature. Thisadditional cooling may be done for example, but not limited to by air orwater cooling.

An inner vessel lid 125 covers the inner vessel 120 but does nothermetically seal the inner vessel 120 from the outer vessel 110. Whenthe lid 125 is in place, the inner vessel 120 is not sealed from theouter vessel and the pressure between the inner vessel 120 and the spacebetween the inner vessel 120 and the outer vessel 110 is equilibrated.The lid 125 may have one or more holes, or valves, for example but notlimited to flapper valves or the like that allow the pressure in theinner vessel 120 and the pressure between the inner vessel 120 and theouter vessel 110 to equilibrate. Such a setup also prevents or minimizesany damage to the inner vessel 120 if the pressure in it is changedquickly (i.e. the steam is vented). The holes or valves allow pressurebetween the inner vessel 120 and the outer vessel 110 to equilibratethroughout the reaction.

A heat source 130 is used to heat the liquid 115 in the inner vessel120. The heat source 130 may be any suitable heat source suitable forheating liquid in a reactor. For example, a flanged over-the-sideimmersion heater may be used or a band heater may be used which heatsthe outside of the inner vessel 120. Alternatively, external heating ofthe liquid 115 may be carried out using for circulation heaters wherethe liquid 115 is pumped out of the reactor 100, heated externally (byelectricity, gas, etc.), and then pumped back into the inner vessel 120.Alternatively, a vapour injector for injecting heated vapour may used asdescribed in co-pending Canadian patent application 2,582,815 which isincorporated herein by reference.

As will be discussed in more detail below, steam from the liquid 115 inthe inner vessel 120 condenses on the outer vessel 110 during a reactioncooling the outer vessel 110. An optional pump 170 may be used tore-circulate liquid that condenses on the walls of the outer vessel 110using piping 160.

The reactor 100 uses a non-condensable gas between the vessels 110 and120 to limit the condensation of steam onto the inside wall of the outervessel 110 and thereby limit the heating of the outer vessel 110 by thesteam and negate the increase in the operating pressure of the reactorby the addition of the non-condensable gas. Non-condensable gases aregases that will not condense on the walls of the outer vessel 110 underthe operating conditions (temperature and pressure) of the reactor 100.They may be supplied as compressed gas at room temperature and includefor example both inert and non-inert gases and include oxygen, nitrogen,air, argon, methane, ethane, ethylene, hydrogen, helium, carbonmonoxide, nitric oxide, nitrous oxide, and combinations thereof, etc. Toachieve this, the non-condensable gas is substantially partitionedduring operation into the space between the inner 120 and outer vessels110 and the steam is partitioned into the inner vessel 120, therebyreducing or negating the effects of Dalton's Law. A comparative examplewill be used to illustrate these effects as well as the partitioning ofthe non-condensable gas from the steam and the operation of the reactor100.

The inner vessel 120 may be constructed of any suitable material such ascorrosion resistant alloys and alloys having a corrosion resistantcoating. Exotic alloys may be used in the construction of the innervessel 120 as the inner vessel 120 is much thinner than the outer vessel110 and is therefore less expensive to fabricate. A non-limiting exampleof alloys that may be used in fabricating the inner vessel are stainlesssteel, Inconel®, Monel®, hastealloy, etc.

Comparative Example

The following comparative example is illustrative and the Applicant doesnot wish to be bound by theory.

A schematic of a dual reactor that does not partition thenon-condensable gas is shown in FIG. 1. The dual reactor 5 does not havea cover and is used to illustrate one of the problems that has beenovercome with the dual vessel reactor and method of carrying out areaction as described herein with references to FIGS. 2 and 3. Thereactor 5 has water in the inner reactor and the remainder of the spaceis filled by pressurized nitrogen. For example, the nitrogen has beenset at a pressure that will create a partial pressure of 150 psi (1034kpa) when the water has been heated to a certain temperature (forexample 180° C.). When the water is heated to this temperature, thesteam creates a partial pressure of water of 150 psi (1034 kpa). UsingDalton's Law the pressure in the vessel would then be 300 psi (2068kpa). It can be seen from this example that it is not desirable to addnitrogen or other non-condensable gases, to the vessel as it increasesthe operating pressure of the vessel and thus the cost of the vessel ashigher operating pressures require thicker metal in construction of theouter pressure vessel.

In a reactor such as that described herein, for example with referenceto FIG. 2, non-condensable gas, such as nitrogen, is added to thereactor in FIG. 2 via for example an input 200 from a non-condensablegas reservoir 180, for example through the use of a valve 190. It willbe appreciated that the non-condensable gas may be added to the reactor100 using any suitable method and the reactor design is not limited tothe method or apparatus for inputting the non-condensable gas. Thenon-condensable gas may be introduced through a series of valves (whichmay or may not be computer controlled), with pressure gauges to monitortheir pressure. Introducing the non-condensable gas by computer controlis the preferable method when introducing the non-condensable gas duringthe reaction. The non-condensable gas is added, for example, so that itwill generate a pressure of approximately 150 psi (1034 kpa) when thenitrogen has been substantially partitioned in the space between theinner vessel 120 and the outer vessel 110. As the liquid 115 is heatedin the inner vessel 120 to a point where the steam generates a pressureof 150 psi (1034 kpa) it builds up a pressure of steam in the innervessel 120 and this pushes the non-condensable gas from the inner vessel120 to the space between the vessels 120 and 110 (i.e. the steamsubstantially partitions the non-condensable gas into the space betweenthe inner vessel 120 and the outer vessel 110 and the steam into theinner vessel 120). The partitioning process is a dynamic process. As theliquid is heated, and steam is generated, a mixture of non-condensablegas and steam flow out of the inner vessel 120 into the space betweenthe inner 120 and outer vessel 110. However, because the walls of theouter vessel 110 are cooler than the steam, the steam condenses on them.When the steam condenses it reduces the pressure between the inner 120and outer vessels 110 and this causes even more steam and nitrogen toflow out of the inner vessel 120. In this way the steam that enters thespace between the inner 120 and outer 120 vessels continues to condenseon the cooler walls of the outer reactor and eventually drives most ofthe non-condensable gas into the space between the inner 120 and outer110 vessels partitioning the steam into the inner vessel 120 and thenon-condensable gas into the space between the two vessels 110 and 120.The non-condensable gas in the space between the inner 120 and outer 110vessels then acts as an insulator between the inner 120 and outer 110vessels limiting heat transfer and maintains the outer vessel 110 coolerthan the inner vessel 120 without steam continuously condensing on it asin FIG. 1. A situation is achieved where the pressure in the spacebetween the inner 120 and outer 110 vessels is about 150 psi (1034 kpa)(mainly from non-condensable gas) and an equal pressure is observedinside the inner vessel 120 (mainly from steam).

If necessary, the outer vessel 110 may be cooled using an externalcooling device.

FIG. 4 depicts in a schematic an inner vessel 400 that may be used asthe inner vessel 120 of a reactor as described above. FIGS. 5 and 6depict in schematics cross sections of the inner vessel 400 taken alonglines A-A′ and B-B′ respectively. The inner vessel 400 has an outershell 402 and an inner shell 404. The inner shell 404 is covered by acover 406. The inner shell 404 is not sealed by the cover 406, andliquid is able to freely pass between the inner shell 404 and the outershell 402. The inner shell 404 provides a container where reactions maytake place.

The outer shell 404 is covered with a lid 408. The lid 408 has a collar409 that seals the interior of the inner vessel 400; however, the lid408 also includes passageways 412 that allow vapour, non-condensablegas, or a combination of the two to pass between the interior of theinner vessel 400 and the exterior of the inner vessel. The passageways412 allow the interior of the inner vessel to be at a similar pressureas the interior of the outer vessel, which it is enclosed in.

The inner vessel includes a plurality of ports 410, 414, 416. Ports 410may be used to exhaust vapour or steam from the interior of the innervessel 400 once the reaction is completed. This exhaust may be used, forexample, to preheat other reactions occurring in other reactors.Exhausting the vapour through ports 410 helps to cool down the innervessel 400 once the reaction is completed. Ports 414 may be used asinlet ports to fill the inner vessel with the required liquid andpossibly any other reactants, required for the reactions. Port 416 maybe used as an outlet for emptying the liquid from the interior of theinner vessel. The port 416 may also be used to circulate, and possiblyheat, the liquid in the interior of the inner vessel 400. The liquidcould, for example, be circulated from the port 416 and input back intothe inner vessel 400 via one of the ports 414.

A heater 418 comprising a plurality of heating elements 420 is suspendedin the inner shell 404. The heater 418 is fixed to a flange 422 on theouter shell 402. The heater 418 may be fixed to the flange using, forexample, bolts. The flange 422 allows an electrical wire 424 to passthrough the outer shell 402, while maintaining the integrity of theouter shell 402.

The inner vessel 400 may be seated on a bottom surface of the outervessel, depicted as 428 in FIG. 4. The inner vessel may be raised off ofthe bottom surface 428 by a supporting structure, such as for example,support legs 426.

FIG. 7 depicts in a flow chart a method 700 of maintaining an outervessel at a temperature below a reaction temperature. The method may beused to maintain the temperature of the outer vessel while carrying outa reaction in a dual vessel chemical reactor. The method begins withadding a non-condensable gas to the dual vessel reactor (702). Theamount of non-condensable gas added may vary depending on the type ofcontrol used during the reaction. For example, a final amount ofnon-condensable gas may be added at the start, in which case furthernon-condensable case does not need to be added during the reaction.Alternatively a lower amount of non condensable gas may be addedinitially, and additional non condensable gas added during the reactionprocess. Regardless of the type of control used, an initial amount ofnon-condensable gas is added to the dual vessel reactor. With thenon-condensable gas added, the liquid in the inner vessel is heated(704). The heating of the liquid brings the liquid temperature up to areaction temperature. Vapour is formed from the heated liquid. Thenon-condensable gas and vapour is partitioned so that the vapour issubstantially partitioned inside the inner vessel (704). Thispartitioning of the vapour to the interior of the inner vessel preventsvapour from condensing on the wall of the outer vessel, which wouldraise the temperature of the outer vessel.

The vapour is partitioned as a result of the non-condensable gas. Thepartial pressure of the non-condensable gas is maintained above thepartial pressure of the vapour, which in combination with thepassageways between the inner and outer vessels restricts the vapourfrom escaping the interior of the inner vessel.

FIG. 8 depicts in a flow chart, a method 800 similar to method 700;however, the method 800 further comprises monitoring the temperature ofthe reaction to maintain a pressure differential between thenon-condensable gas and the vapour. The method begins with adding aninitial amount of non-condensable gas to the dual vessel reactor (802)and then heating the liquid (804) up to a reaction temperature. Themethod monitors the liquid temperature (806) and determines if thereaction is complete (808). If the reaction is complete (Yes at 808) themethod ends. If the reaction is not complete (No at 808), the methoddetermines a vapour partial pressure (P_(V)) that results from theliquid temperature (810). The method then determines if the partialpressure of the non-condensable gas (P_(nc)) is less than or equal toP_(V) plus a pressure differential (Δ_(pres)) that is to be maintained(812). If it is less than or equal to (Yes at 812) then morenon-condensable gas is added to the dual vessel reactor (814) to restorethe desired pressure differential. The method then returns to monitorthe temperature of the liquid (806). If P_(nc)>P_(V)+Δ_(pres) (No at812) the method returns to monitor the temperature of the liquid (806).

It will be appreciated that the above methods may be used to carry outvarious chemical reactions. The inner vessel may hold solid or largereactants, while further reactants may be added to the liquid that isheated.

Experimental Examples

A series of experiments have been performed validating the conceptoutlined above using a non-condensable gas in the space between the twovessels 110 and 120 thereby allowing the outer vessel 110 of the reactor100 to run at a temperature that is much cooler than the inner vessel120. The results of the experiments are shown in FIG. 3.

In the experiments, a pressure vessel (outer vessel 110) was used thatis 36 inches diameter and 10 ft long, and rated at 150 psi (1034 kpa).It has an inner vessel 120 that can hold approximately 800 L of liquid(in this case water). The water is heated with an immersion heater 130.Any open spaces between the inner 120 and outer 110 vessels wereminimized and two flapper valves installed in the lid 140 to allow thepressure to equilibrate between the vessels 110 and 120.

In the series of experiments water was heated in the inner vessel 120from 25° C. to 180° C. and held there for 1 hour. Preset pressures ofnitrogen were used (e.g. 40 psi (276 kpa) at 25° C.) and the temperatureof the water and pressure was monitored in the vessel 120 as the waterwas heated to 180° C. The results are shown in FIG. 3 along with thevapour pressure curve for water.

It can be seen that the curves for the experiments with startingpressures up to 60 psi (414 kpa) merge with the curve for water but thatthe curve for the starting pressure of 95 psi (655 kpa) does not mergeand is much higher.

The experimental data has been supplemented with computer modeling. Forthe experimental set up (i.e. volumes of the inner 120 and outer 110vessels that contain non-condensable gas, etc) there is a cross overpoint. That is, at a starting pressure of about 70 psi (483 kpa) ofnon-condensable gas such as nitrogen, and at the end point, that is 180°C., all the nitrogen that is in the inner vessel 120 has been purged outof the inner vessel 120 and the pressure of nitrogen in the spacebetween the inner 120 and outer 110 vessels (which now contains thenitrogen that was originally in this space plus the nitrogen purged fromthe inner reactor) equals the pressure of the steam in the inner vessel120. That is the steam and the nitrogen has been partitioned.

It must be stressed that even though the reactor was started with apressure of 70 psi (483 kpa) of nitrogen, the final pressure was 150 psi(1034 kpa), which is also the saturated vapour pressure of the water at180° C., and this means that there was no nitrogen left in the innervessel otherwise (through Dalton's Law) the pressure would have beenhigher.

For non-condensable gas starting pressures above 70 psi (483 kpa), it isnot possible to purge all of the non-condensable gas out of the innervessel 120 because it would result in a pressure between the vessels 110and 120 that exceeds the steam pressure in the inner vessel 120. Part ofthis “surplus” remains in the inner vessel 120 and results in pressuresthat exceed the vapour pressure of water (see 95 psi (655 kpa) curve).

For non-condensable gas starting pressures below 70 psi (483 kpa), thereis not sufficient non-condensable gas to fill the space between the twovessels 110 and 120 with non-condensable gas at 150 psi (1034 kpa) whenthe water is heated to 180° C. and there is what will be referred to asa “deficit” in non-condensable gas in the space between the vessels 110and 120. This deficit is taken up by steam which can condense on thewalls of the outer vessel 110 if the walls are cooler than the steamtemperature. The bigger the deficit, the larger the heat flow to theouter reactor will be as steam condenses on it. For example, during thecourse of the experiment an additional 25 L of water condensed on thewalls when the starting pressure was 8 psi (55 kpa) versus 60 psi (414kpa).

Therefore, for the experiments used above, a useful starting pressure isabout 70 psi (483 kpa). Under these conditions, and without any coolingto the outer vessel 110, the temperature rise of the vessel 110 waslimited to 40° C. versus 155° C. if the non-condensable gas had not beenthere.

Even though the procedure described above limited the temperature riseto about 40° C. most of the heating that occurred came from the factthat steam is also purged out of the inner vessel 120 along with thenon-condensable gas. This can be minimized further by adding thenon-condensable gas as the water is actually being heated (not beforethe experiment) so that, for example, a surplus pressure ofnon-condensable gas of 10 psi (69 kpa) is maintained (i.e. 10 psi (69kpa) over the equivalent steam pressure), and it is not thereforenecessary to purge the non-condensable gas out of the inner vessel 120as the water is heated.

Illustrative Processes for Carrying out a Reaction

Taking a broader look at the process, some options for adding thenon-condensable gas are but are not limited to:

-   -   1. Start with 150 psi (1034 kpa) and vent gas as the pressure        rises.    -   2. Start with pressures ideally around the cross-over point.    -   3. To add non-condensable gas as the liquid is heated to        maintain an excess pressure (over that of steam).

In options 1 and 2 the non-condensable gas is added and the vapourpushes it out of the inner vessel 120 into the space between the innervessel 120 and the outer vessel 110. The process of pushing thenon-condensable gas out of the inner vessel 120 also results in thetransfer of steam into the space between the vessel 110 and 120 followedby the condensation of the steam onto the outer vessel 110. In option 3this transfer is limited by adding the non-condensable gas as it isneeded. A small pressure (for example 10 psi) of the non-condensable gasis used at the start of the process in the reactor 100. As the liquid115 is heated and the pressure of the steam in the inner reactor rises,non-condensable gas is added to the space between the vessels 110 and120 to maintain a pressure that is above the pressure of the steam inthe inner vessel 120. For example, the excess pressure may be 10 psi. Inthis way, the non-condensable gas is purged out of the inner vessel 120and heat transfer from the steam that accompanies it is minimized. The10 psi is an example of what could be used for lower pressure reactions(for example up to 150 psi) but this pressure could be much higher foroperations at higher pressures. It will be appreciated that the vapourpressure of the liquid 115 may be determined by measuring itstemperature as it is being heated and computing its vapour pressure.

In terms of how well the inner vessel 120 is sealed, originally halfinch of space around the immersion heater flange was provided. Thisresulted in an open space (to the outer vessel 110) of about 14 in² (90cm²). Under equivalent test conditions this open space caused anadditional 12 L of water to condense during the experiment mentionedabove.

Although the examples above use a pressure of 150 psi, the reactor 100may operate at much higher pressures of 500 psi or 1000 psi as necessaryfor carrying out a specific reaction. The concept of partitioning thenon-condensable gas from the steam for cooling the outer vessel 110applies at high pressures as well and the examples above are merelyillustrative and not limiting. The thickness of the pressure vesselincreases as the pressure increases. Reaction pressures of up to 2,000psi may be carried out in a reactor as described herein.

The devulcanization of rubber may be carried out in a reactor asdescribed herein at a reaction pressure of not over 2000 psi and areaction temperature of not over 350° C. The outer vessel 110 is keptcool by minimizing thermal contact between the two vessels 110 and 120and by insulating the inner vessel 120 from the outer vessel 110 usingthe partitioned non-condensable gas and the vapour as described above.Some heat transfer through the non-condensable gas between the vessels110 and 120 is observed, and of course any steam that condenses on theouter vessel 110 transfers heat. The condensation of steam can bereduced by introducing the non-condensable gas during the reaction andmaintaining an excess pressure of the non-condensable gas over the steamas outlined in option 3 above. In one embodiment, the non-condensablegas is introduced by computer control.

The present invention has been described with regard to a plurality ofillustrative embodiments. However, it will be apparent to personsskilled in the art that a number of variations and modifications can bemade without departing from the scope of the invention as defined in theclaims.

1. A dual vessel chemical reactor comprising: an outer vessel; a reactorlid on the outer vessel, the reactor lid openable for accessing theinner vessel; an inner vessel within the outer vessel for containing aliquid, the inner vessel in atmospheric communication with the outervessel; a heat source for heating a liquid in the inner vessel; a sealfor sealing the reactor lid with the outer vessel when in a closedposition; an inner vessel lid for covering the inner vessel; whereinduring operation a non-condensable gas is used to substantially insolatethe outer vessel from the inner vessel.
 2. The reactor of claim 1,wherein the reactor further comprises: a non-condensable gas input forinputting the non-condensable gas into the outer vessel.
 3. The reactorof claim 2, wherein the reactor further comprises: a non-condensable gasreservoir in communication with the non-condensable gas input; and avalve for opening and closing the non-condensable gas input into theouter vessel.
 4. The reactor of claim 1, further comprising a passage inthe inner vessel, the inner vessel lid or between the inner vessel lidand the inner vessel for bringing the inner vessel into atmosphericcommunication with the outer vessel.
 5. The reactor of claim 4, whereinthe passage comprises a valve.
 6. The reactor of claim 5, wherein thevalve is a flapper valve.
 7. The reactor of claim 1, wherein the seal isone of: a metal seal, a rubber o-ring seal, or a composite gasket. 8.The reactor of claim 1, wherein the seal is a rubber o-ring seal.
 9. Thereactor of claim 8, wherein the rubber o-ring seal comprises one ofethylene propylene diene M-class rubber (EPDM), Silicone rubber,Kalrex®, polyacrylate, Viton®, flurosilicone or Aflaf™.
 10. The reactorof claim 1, wherein the outer vessel is maintained at or below 225° C.during operation of the reactor temperature.
 11. The reactor of claim 1,wherein the outer vessel is made from a corrosion resistant alloy. 12.The reactor of claim 11, wherein the corrosion resistant alloy is one ofstainless steel, Inconel® or Monel®.
 13. The reactor of claim 1, whereinthe outer vessel is made from an alloy coated with a coating selectedfrom the group consisting of: paint, enamel, plasma, thermal,galvanized, plating and weld cladding.
 14. The reactor of claim 1,wherein the inner vessel and the inner vessel lid are separated by anopening to allow pressure between the inner vessel and the outer vesselto equilibrate during operation of the reactor.
 15. The reactor of claim1, wherein the inner vessel and the inner vessel lid are separated usinga flapper valve to allow pressure between the inner vessel and the outervessel to equilibrate during operation of the reactor.
 16. A method ofmaintaining an outer vessel at a temperature below a reactiontemperature while carrying out a reaction in a dual vessel chemicalreactor, the dual vessel chemical reactor having an inner vessel inatmospheric communication with the outer vessel and substantiallypartitionable from the outer vessel, the method comprising the steps of:a) adding a non-condensable gas to the reactor; b) heating a liquid inthe inner vessel to generate a vapour; and c) substantially partitioningthe non-condensable gas in the outer vessel and the vapour in the innervessel.
 17. The method of claim 16, wherein the non-condensable gas ismaintained at an excess pressure relative the vapour pressure of theliquid in the inner vessel as the liquid is heated.
 18. The method ofclaim 17, wherein the non-condensable gas is added to the space betweenthe inner vessel and the outer vessel during the reaction to maintainthe excess pressure relative the vapour pressure of the liquid therebypartitioning the non-condensable gas in the outer vessel and the vapourin the inner vessel.
 19. The method of claim 16, wherein step thenon-condensable gas is portioned in the outer vessel and the vapour inthe inner vessel by condensing the vapour in the space between the outervessel and the inner vessel on the outer vessel.
 20. The method of claim16, wherein the non-condensable gas is added to the reactor before stepb).
 21. The method of claim 16, wherein the non-condensable gas is addedat a predetermined pressure so that after step c) the non-condensablegas is at a reaction pressure.
 22. The method of claim 16, wherein thenon-condensable gas is one or a combination of oxygen, nitrogen, air,argon, methane, ethane, ethylene, hydrogen, helium, carbon monoxide,nitric oxide or nitrous oxide.
 23. The method of claim 16, wherein thenon-condensable gas is nitrogen.
 24. A method of carrying out a chemicalreaction in a dual vessel chemical reactor, the dual vessel chemicalreactor having an inner vessel in atmospheric communication with theouter vessel and substantially partitionable from the outer vessel, themethod comprising the steps of: a) adding a non-condensable gas to thereactor; b) adding a reactant to a liquid in the inner vessel; c)heating the liquid in the inner vessel to generate a vapour; and d)substantially partitioning the non-condensable gas in the outer vesseland the vapour in the inner vessel.
 25. The method of claim 24, whereinthe chemical reaction is the devulcanization of rubber.
 26. The methodof claim 25, wherein the non-condensable gas is maintained at an excesspressure relative the vapour pressure of the liquid in the inner vesselas the liquid is heated.
 27. The method of claim 26, wherein thenon-condensable gas is added to the space between the inner vessel andthe outer vessel during the reaction to maintain the excess pressurerelative the vapour pressure of the liquid thereby partitioning thenon-condensable gas in the outer vessel and the vapour in the innervessel.